1. Field of the Invention
The present invention relates generally to methods for detecting horizontal wind shear within a geographic location of an airport bounded by a network of sensors located at specific locations. More particularly, the invention relates to wind shear detection systems Which incorporate a network of anemometers to sense wind velocity, speed and direction, near the airport.
2. Description of the Prior Art
The Federal Aviation Administration (FAA) has previously deployed a Low Level Wind Shear Alert System (LLWAS). The LLWAS used sensors or anemometers on towers located at specific locations about an airport. The anemometers measured wind velocity. The original LLWAS system gave information to the air traffic controllers, which information was relayed by radio to the pilot of an arriving or departing aircraft.
The original LLWAS system used a vector difference algorithm to detect horizontal wind shear, i.e., wind shears which affected head wind relative to an aircraft. The LLWAS system issued general area messages about wind shear and was not geographic specific within the wind field about the airport. A wind field is made up of wind velocity vectors for each sensor station over the geographic area in which a network of sensors is established. The LLWAS did not issue runway specific messages and did not estimate the intensity of the wind shear hazard.
A follow-up system to LLWAS, called a Phase II system, has been developed by the FAA to upgrade LLWAS. The Phase II system uses the same anemometers to provide wind velocity and direction data. The Phase II system is partially adapted to handle data noise. The Phase II system has a limited ability to detect wind field divergence, a derived value based on spacial derivatives of the wind field. Specifically, a positive divergence might indicate a microburst wind shear, or a less intense wind shear. Divergence is associated with a loss of head wind, and resulting loss of aircraft performance on takeoff or landing.
Even though the Phase II system attempts to detect wind field divergence, neither LLWAS nor the Phase II system is capable of issuing microburst alarms, as differentiated from any other wind shear. The Phase II system does not give runway specific information about the intensity or location of any wind shear, other than a general regional statement. The Phase II system is the wind shear alert system operating throughout the United States at the present time.
Both the original LLWAS and the Phase II system use the same basic approach. Anemometer data is gathered and processed for the network. A simple wind shear alert, without differentiating between a microburst and other wind shear, is given for a general location. The locations are directional, i.e., north or east. The magnitude of the wind shear hazard, i.e., whether a microburst is present, and its location are not addressed in the prior systems.